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AdBlue Leak Or White Crystals

White crystals or a crusty deposit around the AdBlue filler, tank, pump or lines usually means a small AdBlue (DEF) leak; the fluid dries into crystals.

Normal risk

Have it checked soon. AdBlue faults can lead to warnings and a no-start countdown on many diesels.

Short answer · Why are there white crystals around my AdBlue system?

AdBlue is a urea solution that crystallises as it dries. A little crust around the filler after topping up is normal and can be rinsed with water. Crystals around the pump, lines or the injector in the exhaust point to a leak. Leaks can cause low-level, pressure or quality warnings, and the car may limit restarts until fixed.

On this page

Safe checks you can do

  1. Rinse the filler areaClean crystals with warm water after topping up.
  2. Look under the carCheck the tank, pump and lines for crystals or wet areas.
  3. Check the dashboardAdBlue warnings and a countdown need attention.

Questions that narrow it down

  1. Is there an AdBlue warning on the dash?Read the codes.
  2. Did you spill while filling?Normal crust; rinse it off.
  3. Are there crystals at the exhaust injector?A leak or blocked injector.

Possible causes

Listed without ranking. Use the questions above to see which ones fit your car.

  1. Spillage when fillingHarmless if rinsed.
  2. Leaking AdBlue lineCrystals along the line.
  3. Pump or tank sealCrystals at the tank.
  4. Exhaust injector leakCrust around the dosing unit.

Questions about AdBlue Leak Or White Crystals

Is AdBlue harmful?

It is not toxic in normal handling, but it is corrosive to some metals. Rinse spills with water.

Can the car stop starting because of AdBlue?

Many diesels limit restarts if the AdBlue system has a fault or is empty.